CD19 and rheumatoid arthritis: In particular, miR-223-3p, which had significantly increased expression in CD19+ B cells from our MTX treated RA patients, has been widely studied and reported to be upregulated in other cell types, i.e. macrophages, monocytes and CD4+ T cells (18, 45, 46), and proposed to regulate the formation of osteoclasts in RA synovium (45).